2004 Mazda 3 Starting

We just drove from Houston to Phoenix in a Mazda 3. Every time we stopped to fill the gas tank, it would not immediately start, it would crank but not fire. After sitting for 20 minutes, it would then start and we'd be on our way. When we stopped for other reasons, it would start with no problem. Could it be that when we took the cap off the gas tank and released pressure in the fuel system we where getting vapor lock in the fuel line at the hot engine? The car ran and drove fine otherwise throughout the trip.

Could this be a problem with a check valve in the line between the fuel pump and engine (if there is one) or a weak fuel pump?